This invention relates to a boring tool having at least two cutter elements for achieving separate cutting actions during insertional movements and retractive movements of the tool into or out of a hole in a work piece. During insertional movement of the tool into a hole in a work piece a first one of the cutter elements performs a relatively rough machining operation on the hole surface. During retractive movement of the tool out of the hole, a second cutter element performs a finish cut on the hole surface.
While the tool is at the limit of its insertional movement in the hole in the work piece an adjusting operation is performed, whereby the second cutter element is advanced radially outwardly away from the tool rotational axis. The second cutter element is thus free to perform a machining operation on the hole surface without interference by the first cutter element. During insertional movement of the tool into the hole in the work piece the second cutter element is adjusted radially inwardly so as not to interfere with the cutting action of the first cutter element.
The present invention is preferably embodied as a tool that includes a tool clamping unit constructed as shown in U.S. Pat. No. 5,193,954 issued to Carl Hunt on Mar. 16, 1993. U.S. Pat. No. 5,193,954 discloses a mechanism for releasably clamping a cutter element holder to a cutting machine or spindle. The clamping mechanism includes a support housing having a frusto-conical socket adapted to receive therein a protruding section of the cutting element holder. An elongated, movable, tubular clamping bar is located within the housing for the purpose of moving an array of wedge lock elements outwardly against internal lock surfaces on the protruding section of the cutting element holder, such that the cutting element holder is firmly clamped to the housing. Reverse motion of the tubular clamping bar unlocks the wedge lock elements, so that the cutting element holder can be removed from the housing.
The present invention can be constructed to include a cutter element adjustment structure having mating components carried by the support housing and the cutting element holder. An elongated actuator rod extends within the tubular clamping bar so as to be releasably connectable to a slide element located in the cutting element holder. A transverse (radial) pin extends between the slide element and one of the cutter elements, whereby axial movement of the slide element translates into radial motion of the cutter element.
The cutter element adjustment structure Of the present invention is designed to be operated automatically from a remote point within the cutting machine, such that the desired adjustment of the cutter element is achieved quickly by automatic control means at a predetermined point in the cutting cycle, e.g. when the cutter element holder is fully inserted into the hole in the work piece, and prior to retractive movement of the cutter element holder out of the work piece. After the cutter element has been withdrawn from the work piece the adjustment structure is operated to return the adjustable cutter element to a non-interfering position relative to the other cutter element.
A principal object of the invention is to provide a cutter element adjustment means that can be operated remotely and automatically at predetermined points in a hole boring cycle, whereby two separate cutting actions can be performed by different cutter elements while the tool is advancing into the hole and subsequently while the tool is being retracted out of the hole. The adjustment means is designed to achieve a predetermined radial adjustment of the associated cutter element, so as to facilitate the attainment of a precision surface on the work piece hole.